Fuel efficiency based integrated engine firing fraction and transmission ratio selection

ABSTRACT

A fuel management system includes a memory and a control module. The memory stores fuel rate maps for multiple firing fractions, where: each of the firing fractions corresponds to a respective firing pattern of an engine; at least some of the firing patterns include deactivating one or more cylinders. The control module: for each of the firing fractions, determines a fuel efficiency value for each of multiple transmission gear ratios, where fuel efficiency values are provided for transmission ratio and firing fraction pairs; applies drive ability constraints to provide resultant transmission ratio and firing fraction pairs; subsequent to applying the drive ability constraints and based on the fuel efficiency values, selects one of the resultant transmission ratio and firing fraction pairs; and concurrently operates a transmission and the engine according to the selected one of the transmission ratio and firing fraction pairs.

INTRODUCTION

The information provided in this section is for the purpose of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent it is described in this section, as well asaspects of the description that may not otherwise qualify as prior artat the time of filing, are neither expressly nor impliedly admitted asprior art against the present disclosure.

The present disclosure relates to active and dynamic fuel managementsystems of a vehicle.

Coordinated torque control systems are used to control engine andtransmission output torques to satisfy various torque demands of avehicle. Full authority active fuel management (FAAFM) and dynamic fuelmanagement (DFM) systems coordinate deactivation of one or more selectedcylinders of an engine to improve fuel economy. The fuel managementsystems determine, based on fuel economy, which cylinders to deactivatewhile satisfying torque demands. Cylinder deactivation may includeclosing and/or disabling movement of intake and exhaust valves anddisabling spark and supply of fuel to the deactivated cylinders.

SUMMARY

A fuel management system is provided and includes a memory and a controlmodule. The memory is configured to store m fuel rate maps respectivelyfor m firing fractions, where: each of the m firing fractionscorresponds to a respective firing pattern for cylinders of an engine ofa vehicle; at least some of the firing patterns include deactivating oneor more of the cylinders; and where m is an integer greater than orequal to two. The control module is configured to: for each of the mfiring fractions, determine a fuel efficiency value for each of ntransmission gear ratios, where n*m fuel efficiency values are providedfor n*m transmission ratio and firing fraction pairs; applying driveability constraints to the n*m transmission ratio and firing fractionpairs to provide resultant transmission ratio and firing fraction pairs;subsequent to applying the drive ability constraints and based on thefuel efficiency values of the resultant transmission ratio and firingfraction pairs, select one of the resultant transmission ratio andfiring fraction pairs; and concurrently operate a transmission and theengine according to the selected one of the transmission ratio andfiring fraction pairs.

In other features, the control module is configured to select the one ofthe resultant transmission ratio and firing fraction pairs based on acost function, which is directly related to fuel efficiency. The costfunction is based on a fuel rate, an engine power, and a transferefficiency.

In other features, the control module is configured to: for each of them firing fractions, determine a transfer efficiency value for each ofthe n transmission gear ratios; and determine each of the n*m fuelefficiency values based on a respective one of the transfer efficiencyvalues.

In other features, the control module is configured to determine each ofthe transfer efficiency values based on a respective engine speed andengine torque pair.

In other features, the control module is configured to: for each of them firing fractions, determine a fuel rate for each of the n transmissiongear ratios; and determine each of the n*m fuel efficiency values basedon a respective one of the fuel rates.

In other features, the control module is configured to determine each ofthe fuel rates based on a respective one of multiple engine speed andengine torque pairs.

In other features, the control module is configured to: in response todetermining one of the engine speed and engine torque pairs is outsideof an operable range, assign a predetermined default fuel rate value fora corresponding one of the n*m transmission ratio and firing fractionpairs; and refrain from selecting the one of the n*m transmission ratioand firing fraction pairs based on the predetermined default fuel ratevalue.

In other features, the control module is configured to: for each of them firing fractions, determine an engine speed and engine torque pair foreach of the n transmission gear ratios; determine a transfer efficiencyvalue for each of the engine speed and engine torque pairs; anddetermine the n*m fuel efficiency values based respectively on thetransfer efficiency values.

In other features, the control module is configured to: determine aturbine speed and turbine torque pair of a torque converter for each ofthe n transmission gear ratios; for each of the m firing fractions andbased on an amount of torque converter slip and the turbine speed andturbine torque pairs, determine an engine speed and engine torque pairfor each of the n transmission gear ratios; determine a transferefficiency value for each of the engine speed and engine torque pairs;and determine the n*m fuel efficiency values based respectively on thetransfer efficiency values.

In other features, the drive ability constraints include at least oneof: limiting output torque to a maximum amount of engine output torque;limiting, for each of the m firing fractions, engine speed to be withina range between a minimum engine speed and a maximum engine speed;preventing concurrent deactivation of a predetermined combination of thecylinders; preventing a predetermined order of activating selected onesof the cylinders; or preventing a predetermined order of deactivatingselected ones of the cylinders.

In other features, a fuel management method is provided and includes:storing in a memory m fuel rate maps respectively for m firingfractions, where: each of the m firing fractions corresponds to arespective firing pattern for cylinders of an engine of a vehicle; whereat least some of the firing patterns include deactivating one or more ofthe cylinders; and where m is an integer greater than or equal to two.The method further includes: for each of the m firing fractions,determining a fuel efficiency value for each of n transmission gearratios, where n*m fuel efficiency values are provided for n*mtransmission ratio and firing fraction pairs; applying drive abilityconstraints to the n*m transmission ratio and firing fraction pairs toprovide resultant transmission ratio and firing fraction pairs;subsequent to applying the drive ability constraints and based on thefuel efficiency values of the resultant transmission ratio and firingfraction pairs, selecting one of the resultant transmission ratio andfiring fraction pairs; and concurrently operating a transmission and theengine according to the selected one of the transmission ratio andfiring fraction pairs.

In other features, the fuel management method further includes selectingthe one of the resultant transmission ratio and firing fraction pairsbased on a cost function, which is directly related to fuel efficiency.The cost function is based on a fuel rate, an engine power, and atransfer efficiency.

In other features, the fuel management method further includes: for eachof the m firing fractions, determining a transfer efficiency value foreach of the n transmission gear ratios; and determining each of the n*mfuel efficiency values based on a respective one of the transferefficiency values.

In other features, the fuel management method further includesdetermining each of the transfer efficiency values based on a respectiveengine speed and an engine torque pair.

In other features, the fuel management method further includes: for eachof the m firing fractions, determining a fuel rate for each of the ntransmission gear ratios; and determining each of the n*m fuelefficiency values based on a respective one of the fuel rates.

In other features, the fuel management method further includesdetermining each of the fuel rates for a respective one of multipleengine speed and engine torque pairs.

In other features, the fuel management method further includes: inresponse to determining one of the engine speed and engine torque pairsis outside of an operable range, assigning a predetermined default fuelrate value for a corresponding one of the n*m transmission ratio andfiring fraction pairs; and refraining from selecting the one of the n*mtransmission ratio and firing fraction pairs based on the predetermineddefault fuel rate value.

In other features, the fuel management method further includes: for eachof the m firing fractions, determining an engine speed and engine torquepair for each of the n transmission gear ratios; determining a transferefficiency value for each of the engine speed and engine torque pairs;and determining the n*m fuel efficiency values based respectively on thetransfer efficiency values.

In other features, the fuel management method further includes:determining a turbine speed and turbine torque pair of a torqueconverter for each of the n transmission gear ratios; for each of the mfiring fractions and based on an amount of torque converter slip and theturbine speed and turbine torque pairs, determining an engine speed andengine torque pair for each of the n transmission gear ratios;determining a transfer efficiency value for each of the engine speed andengine torque pairs; and determining the n*m fuel efficiency valuesbased respectively on the transfer efficiency values.

In other features, the drive ability constraints include at least oneof: limiting output torque to a maximum amount of engine output torque;limiting, for each of the m firing fractions, engine speed to be withina range between a minimum engine speed and a maximum engine speed;preventing concurrent deactivation of a predetermined combination of thecylinders; preventing a predetermined order of activating selected onesof the cylinders; or preventing a predetermined order of deactivatingselected ones of the cylinders.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1A is an example brake specific fuel consumption map for a firstfiring fraction;

FIG. 1B is an example brake specific fuel consumption map for a secondfiring fraction;

FIG. 2 is a functional block diagram of an exemplary coordinated torquecontrol (CTC) system including a fuel management system in accordancewith the present disclosure;

FIG. 3A is an example brake specific fuel consumption map for a firstfiring fraction illustrating fuel efficiencies for differenttransmission ratios for a constant transmission output power;

FIG. 3B is an example brake specific fuel consumption map for a secondfiring fraction illustrating fuel efficiencies for differenttransmission ratios for a constant transmission output power;

FIG. 4 illustrates a method of operating an engine, a torque converterand a transmission in accordance with the present disclosure;

FIG. 5A is an example brake specific fuel consumption map for a firstfiring fraction with imposed constraints to provide an operable regionfor the firing fraction; and

FIG. 5B is an example brake specific fuel consumption map for a firstfiring fraction with imposed constraints to provide an operable regionfor the firing fraction.

In the drawings, reference numbers may be reused to identify similarand/or identical elements.

DETAILED DESCRIPTION

A fuel management system of a vehicle may select a transmission gear anda firing fraction of an engine to improve fuel efficiency. The enginefiring fraction refers to a cylinder firing pattern. A cylinder firingpattern is indicative of which cylinders are activated and deactivatedand the firing order and timing of the activated cylinders during afiring cycle of the engine. A cylinder is activated when fuel and sparkfor the cylinder are enabled and intake and exhaust valves of thecylinder are active (i.e. enabled to move). A cylinder is deactivatedwhen fuel and spark are disabled. While a cylinder is deactivated, theintake and exhaust valves of that cylinder may be (i) disabled, (ii)held closed, or (iii) enabled and open and close while air is beingpumped in and out of the deactivated cylinder. A firing cycle of a fourstroke engine refers to two cycles of a crankshaft and the spark and nospark pattern of the cylinders of the engine.

As an example, in an eight cylinder engine, a ½ engine firing fractionmay be implemented, where four cylinders are deactivated and the otherfour cylinders are activated for each firing cycle of the engine. Thefiring pattern corresponding to the ½ engine firing fraction may repeatevery two firing cycles of the engine. The same or different cylindersmay be activated during each firing pattern cycle of the engine. Asanother example, a ⅓ engine firing fraction may be implemented with afiring pattern that may repeat every three firing cycles. During eachfiring cycle, three cylinders are activated and five cylinders aredeactivated. Different cylinders may be activated during each of thethree firing cycles. For an eight cylinder engine, there are numerouspossible cylinder firing fractions and firing patterns, especially for afuel management system that is capable of activating and deactivatingeach cylinder independently.

Traditionally, a transmission gear and an engine firing fraction areselected separately. The transmission gear is selected using atraditional shift map that includes selecting a transmission gear basedon, for example, a requested engine output torque and engine speed. Theengine firing fraction is subsequently selected to minimize fuel ratewhile satisfying hysteresis and shift ability constraints. Hysteresisconstraints are implemented to minimize frequency of shifting betweenfiring fractions. Shift ability constraints refer to limitations imposedto minimize noise and vibrations and maintain operating stability.Examples of shift ability constraints include, for a specifictransmission gear, maximum torque values and minimum and maximum enginespeed limits.

FIGS. 1A and 1B show example brake specific fuel consumption (BSFC) maps100, 102 for a first firing fraction (FF) (e.g., FF=1) and a second FF(e.g., FF-½). A BSFC map is a plot of engine torque for engine speedincluding irregularly shaped rings having a common center point. Pointsalong each ring represent a same fuel efficiency. Each BSFC value isequal to a fuel flow rate divided by a torque for a given engine speed.The closer to the center point, the better the fuel efficiency. The mapalso illustrates a maximum torque constraint curve Te_max and minimumand maximum engine speed limits Ne_min and Ne_max. The parameter Terefers to torque in newton-meters (nm). Ne may refer to engine speed inrevolutions-per-minute (RPM). The points of the BSFC map refer toamounts of fuel per unit torque. For the example of FIGS. 1A and 1B,since both of the firing fractions of 1 and ½ satisfy the requestedtorque and imposed constraints, the ½ firing fraction may be selectedover the 1 firing fraction, due to the better fuel efficiency providedby the ½ firing fraction. The traditional approach provides a limitednumber of transmission gear (or ratio) and firing fraction pairs toselect from and thus limits the fuel economy achieved.

The examples set forth herein include a fuel management system thatincreases the transmission ratio and firing fraction pairs available(referred to as the optimization space) and performs a process toconcurrently select a transmission ratio and firing fraction forimproved fuel economy. The selected transmission ratio may refer to atransmission ratio associated with a selected transmission gear and/or aspeed ratio of a rotational input speed of an input shaft (or inputgear) of the transmission to a rotational output speed of an outputshaft (or output gear) of the transmission. The disclosed process may bereferred to as a global optimization process.

FIG. 2 is a function block diagram of an exemplary coordinated torquecontrol (CTC) system 200 including a fuel management system 201. The CTCsystem 200 may be configured for a hybrid electric vehicle and/or aninternal combustion engine (e.g., a spark injection direct injection(SIDI) engine). Although the following embodiment is directed to ahybrid vehicle, the embodiments disclosed herein may be applied tonon-hybrid vehicles. The CTC system 200 includes an engine 202 thatcombusts an air/fuel mixture to produce drive torque for a vehicle basedon a driver input module 204. Air is drawn into an intake manifold 210through a throttle valve 212. A CTC (or engine) control module 214commands a throttle actuator module 216 to regulate opening of thethrottle valve 212 to control the amount of air drawn into the intakemanifold 210. Air from the intake manifold 210 is drawn into cylindersof the engine 202. The engine 202 may include any number of cylinders.The CTC module 214 may elect a firing pattern and instruct a cylinderactuator module 220 to selectively deactivate and activate the cylindersaccording to the firing pattern to improve fuel economy.

Air from the intake manifold 210 is drawn into the cylinder 218 throughan intake valve 222. The CTC module 214 controls the amount of fuelinjected by a fuel injection system 224 that includes one or more fuelinjectors 225. The fuel injection system 224 may inject fuel into theintake manifold 210 at a central location or may inject fuel into theintake manifold 210 at multiple locations, such as near the intake valveof each of the cylinders. Alternatively, the fuel injection system 224may inject fuel directly into the cylinders, as shown.

The injected fuel mixes with the air and creates the air/fuel mixture inthe cylinder 218. A piston (not shown) within the cylinder 218compresses the air/fuel mixture. Based upon a signal from the CTC module214, a spark actuator module 226 energizes a spark plug 228 in thecylinder 218, which ignites the air/fuel mixture. The timing of thespark may be specified relative to the crankshaft angle when the pistonis at its topmost position, referred to as to top dead center (TDC), thepoint at which the air/fuel mixture is most compressed.

The combustion of the air/fuel mixture drives the piston down, therebydriving a rotating crankshaft (not shown). The piston then begins movingup again and expels the byproducts of combustion through an exhaustvalve 230. The byproducts of combustion are exhausted from the vehiclevia an exhaust system 234. Exhaust passes through a catalyst 235.

The intake valve 222 may be controlled by an intake camshaft 240, whilethe exhaust valve 230 may be controlled by an exhaust camshaft 242. Invarious implementations, multiple intake camshafts may control multipleintake valves per cylinder and/or may control the intake valves ofmultiple banks of cylinders. Similarly, multiple exhaust camshafts maycontrol multiple exhaust valves per cylinder and/or may control exhaustvalves for multiple banks of cylinders. The cylinder actuator module 220may deactivate cylinders by halting provision of fuel and spark and/ordisabling their exhaust and/or intake valves.

A CTC module 214 may regulate the position of the intake valve 222and/or the exhaust valve 230 to regulate the quantity of air ingestedand inert residual gases retained in the cylinder(s) 218. The CTC module214 may also adjust operation of the fuel injector(s) 225, such as ONtime or size of injector openings, to increase the amount of fuelinjected into the cylinder(s) 218. The CTC module 214 may also adjustthe timing of the exhaust camshaft(s) corresponding to the change in theA/F mixture.

The crankshaft angle at which the intake valve 222 is opened may bevaried with respect to piston TDC by an intake cam phasor 248. Thecrankshaft angle at which the exhaust valve 230 is opened may be variedwith respect to piston TDC by an exhaust cam phasor 250. A phasoractuator module 258 controls the intake cam phasor 248 and the exhaustcam phasor 250 based on signals from the CTC module 214.

The CTC system 200 may include a boost device that provides pressurizedair to the intake manifold 210. For example, FIG. 1 depicts aturbocharger 260. The turbocharger 260 is powered by exhaust gasesflowing through the exhaust system 234, and provides a compressed aircharge to the intake manifold 210. The turbocharger 260 may compress airbefore the air reaches the intake manifold 210.

A wastegate 264 may allow exhaust gas to bypass the turbocharger 260,thereby reducing the turbocharger's output (or boost). The CTC module214 controls the turbocharger 260 via a boost actuator module 262. Theboost actuator module 262 may modulate the boost of the turbocharger 260by controlling the position of the wastegate 264. The compressed aircharge is provided to the intake manifold 210 by the turbocharger 260.An intercooler (not shown) may dissipate some of the compressed aircharge's heat, which is generated when air is compressed and may also beincreased by proximity to the exhaust system 234. Alternate enginesystems may include a supercharger that provides compressed air to theintake manifold 210 and is driven by the crankshaft.

The CTC system 200 may include an exhaust gas recirculation (EGR) valve270, which selectively redirects exhaust gas back to the intake manifold210. In various implementations, the EGR valve 270 may be located afterthe turbocharger 260. The CTC system 200 may measure the speed of thecrankshaft in revolutions per minute (RPM) using an engine speed sensor280. The temperature of the engine coolant may be measured using anengine coolant temperature (ECT) sensor 282. The ECT sensor 282 may belocated within the engine 202 or at other locations where the coolant iscirculated, such as a radiator (not shown).

The pressure within the intake manifold 210 may be measured using amanifold absolute pressure (MAP) sensor 284. In various implementations,engine vacuum may be measured, where engine vacuum is the differencebetween ambient air pressure and the pressure within the intake manifold210. The mass of air flowing into the intake manifold 210 may bemeasured using a mass air flow (MAF) sensor 286. The MAF sensor 286 maybe located in a housing that includes the throttle valve 212.

The throttle actuator module 216 may monitor the position of thethrottle valve 212 using one or more throttle position sensors (TPS)290. The ambient temperature of air being drawn into the CTC system 100may be measured using an intake air temperature (IAT) sensor 292. TheCTC module 214 may use signals from the sensors to make controldecisions for the CTC system 200.

The CTC module 214 may communicate with a transmission control module294 to coordinate shifting gears in a transmission (not shown). Forexample, the CTC module 214 may reduce torque during a gear shift. TheCTC module 214 may communicate with a hybrid control module 296 tocoordinate operation of the engine 202 and an electric motor 298. Theelectric motor 298 may also function as a generator, and may be used toproduce electrical energy for use by vehicle electrical systems and/orfor storage in a battery. In various implementations, the CTC module214, the transmission control module 294, and the hybrid control module296 may be integrated into one or more modules.

To abstractly refer to the various control mechanisms of the engine 202,each system that varies an engine parameter may be referred to as anactuator. For example, the throttle actuator module 216 can change theblade position, and therefore the opening area, of the throttle valve212. The throttle actuator module 216 can therefore be referred to as anactuator, and the throttle opening area can be referred to as anactuator position.

Similarly, the spark actuator module 226 can be referred to as anactuator, while the corresponding actuator position is an amount ofspark advance. Other actuators include the boost actuator module 262,the EGR valve 270, the phasor actuator module 258, the fuel injectionsystem 224, and the cylinder actuator module 220. The term actuatorposition with respect to these actuators may correspond to boostpressure, EGR valve opening, intake and exhaust cam phasor angles,air/fuel ratio, and number of cylinders activated, respectively.

While electric motor 298 may provide torque in series and/or in parallelwith the torque output of engine 202, it should be appreciated thatother configurations are also contemplated to be within the scope ofthis description. For example, electric motor 298 may be implemented asone or more electric motors that provide torque directly to wheels 300instead of passing through a transmission 302.

The torque of engine 202 and optionally the electric motor 298 may beapplied to a torque converter 299 including a turbine 301, a stator 303,a pump (or impellar) 305, a clutch 307, an input shaft 309 and an outputshaft 311. The turbine may be connected to a flywheel 313 of the engine202. Slip of the clutch is associated with how much the input shaft 309is engaged to drive the output shaft 311. The output shaft 311 isconnected to the transmission 302. The transmission 302 may be anautomatic transmission that switches gears in accordance with a gearchange command from the CTC module 214. The transmission 302 may haveany number of gears with respective transmission gear ratios (or simplytransmission ratios). In one embodiment, the transmission is acontinuously variable transmission (CVT) that is able to seamlesslytransition through a continuous range of gear ratios. An output shaft oftransmission 302 is coupled to an input of a differential gear 304.Differential gear 304 drives axles and wheels 300. Wheel speed sensors306 generate signals that indicate a rotation speed of their respectivewheels 300.

The CTC module 214 estimates an engine output torque to provide based onreceived sensor signals and other parameters described herein. The CTCmodule 214 may adjust position of the throttle, air-fuel ratio, valvetiming, fuel injection, etc. to provide the estimated engine outputtorque. Based on a desired engine output torque, the CTC module 214controls engine devices such that a desired air flow, a desired fuelinjection, and/or a desired spark timing is achieved. The desired engineoutput torque may be based on a vehicle operator (driver) request and/ormay be controller based, such as a torque output request from a cruisecontrol system. In particular, the CTC module 214 controls the torqueoutput of the engine based on the coordinated torque control methods andsystems of the present disclosure.

The sensor signals that are received by the CTC module 214 may includesensor signals from: the MAP sensor 284, the MAF sensor 286, thethrottle position sensor 290, the IAT sensor 292, an accelerator pedalposition sensor 295, or other sensors, such as the engine coolanttemperature sensor 282, the engine speed sensor 280, an ambienttemperature sensor 297, an oil temperature sensor 291, and a vehiclespeed sensor 310, an exhaust or catalyst temperature sensor 312.

The CTC module 214 communicates with the throttle actuator module 216and a cruise control module. The CTC module 214 receives a throttleposition signal from the throttle position sensor 290 and adjuststhrottle position based on the throttle position signal. The CTC module214 may control the throttle 212 using a throttle actuator based on aposition of an accelerator pedal 293. The throttle actuator module 216may include a motor or a stepper motor, which provides limited and/orcoarse control of the throttle position.

The CTC module 214 may also control the throttle 212 using the throttleactuator based on input from the cruise control module, such as an axletorque request. The CTC module 214 also generates an effective pedalposition signal, which represents a throttle position regardless ofwhether the vehicle operator is depressing the accelerator pedal 293 orthe cruise control module is controlling the amount of throttle.

Air mass, volume, and pressure per cylinder may be determined and/orestimated based on signals from the sensors 284, 286. The CTC module 214may determine a throttle area based on a desired MAP and a desired MAF,and may generate a control signal to control the throttle based on thethrottle area. The desired MAP and MAF may be determined based on enginespeed and torque request signals.

The CTC system 200 may further include a barometric pressure sensor 308.The barometric pressure sensor 308 may be used to determineenvironmental conditions, which may be further used to determine adesired throttle area. The desired throttle area may correspond to aspecific throttle position.

The fuel management system 201 may also include a memory 320 storingvarious tables 323, maps 324, firing patterns 326, etc., which may beused while performing the fuel management operations described herein.The tables 323, maps 324 and firing patterns 326 may each be associatedwith one or more of the operations described with respect to the methodof FIG. 4.

The CTC module 214 while performing fuel control management processselects a transmission ratio and a firing fraction to provide based on acost function, which may be represented by equation 1.

$\begin{matrix}{{Cost} = {\frac{{Engine\_ Fuel}{\_ Rate}}{\left( {{Engin\_ Power}*{Transfer\_ Efficiency}} \right)} = \frac{1}{Fuel\_ Efficiency}}} & (1)\end{matrix}$

Engine_Fuel_Rate refers to the fuel rate of an engine as a whole at anymoment in time and may be measured in grams per second (g/s).Engine_Power may refer to output power of an engine at any moment intime and be measured in kilowatts. Transfer_Efficiency refers to powertransfer efficiency of an engine, a torque converter, and atransmission. The transfer efficiency is the efficiency of powertransfer from the engine to an output of the transmission. The powertransfer efficiency may be measured in grams per second kilowatt(g/skw). The CTC module 214 uses a set of drivability constraints tounsure drive quality while pursuing best fuel efficiency. The driveability constraints may include the hysteresis and shift abilityconstraints. Different gears have different torque references fordifferent driveline resonances. To prevent vibrations and/or noises, thedrive ability constraints may also include limiting the number of modes(or firing patterns) to a predetermined set of modes that are morestable than other modes, preventing certain combinations of cylindersfrom being concurrently deactivated, preventing a predetermined order ofactivating selected ones of the cylinders, preventing a predeterminedorder of deactivating selected ones of the cylinders, and/or otherlimitations for noise and vibration reasons. The drive abilityconstraints may also be provided to prevent hard shifts or “clunky”shifting and thus maintain a high quality driving experience.

FIGS. 3A and 3B show BSFC maps 330, 332 for a first FF (e.g., 1) and asecond FF (e.g., ½) illustrating fuel efficiencies for differenttransmission ratios for a constant transmission output power. Some ofthe different transmission ratios are identified with dots 332, 334along constant transmission output power curves 336, 338. In theexamples shown, it is assumed that the transfer efficiency for eachtransmission gear is the same. If the transfer efficiency is differentfor different transmission gears, then curves 336, 338 would bedifferent than shown. Although four dots are shown in FIG. 3A, thetransmission may have more than four gears. Not all gears arerepresented by dots in FIGS. 3A and 3B. The BSFC maps 330, 332 alsoincludes torque maximum Te_max curves and engine speed limits Ne_min andNe_max. FIGS. 3A and 3B also includes torque reserve curves 340, 342.

For the example shown in FIGS. 3A and 3B, the CTC module 214 may selectthe Xth gear and the FF of ½ rather than selecting the X−1 gear and theFF of 1. This is because, for the example shown, the fuel efficiency isbetter for the combination pair of the Xth gear and the FF of ½.Traditionally, however, the lower gear and the FF of 1 may have beenselected. Note that In FIG. 3B, the lower gear is not suitable for theFF of ½ because the corresponding toque level is higher than Te_max andthus is not selectable. The CTC module 314 selects a FF and transmissionratio that minimizes the cost function to maximize fuel efficiency whilesatisfying constraints including hysteresis and shift abilityconstraints.

FIG. 4 illustrates a method of operating an engine, a torque converterand a transmission, such as that shown in FIG. 2. The followingoperations may be iteratively performed and performed by the CTC module214 and/or one or more other modules of FIG. 2. The method may begin at400. At 402, the CTC module 214 may determine vehicle parameters, suchas engine speed, vehicle speed, minimum engine output torque to satisfytorque requests (or total requested output torque), and/or other engine,torque converter, and/or transmission related parameters. Although atleast some of the parameters are referred to below and accounted forduring performance of the following method, other parameters may also beaccounted for such as ambient temperature, engine temperature, and/orother parameters, such as the parameters mentioned above.

At 404, the CTC module 214 may impose constraints on engine fuel ratemaps (e.g., BSFC maps or other fuel rate related maps) to obtainoperable regions for each of multiple different firing fractions. Theengine fuel rate maps are provided that satisfy the minimum engineoutput torque to satisfy the total requested output torque. FIGS. 5A and5B show example BSFC maps 500, 502 for a first firing fraction (e.g.,FF=1) and a second firing fraction (FF=½) with imposed constraints.Although two firing fraction maps are shown, any number of differentfiring fraction maps may be generated, used and/or modified. The BSFCmaps 500, 502 include maximum engine torque curves Te_max, minimum andmaximum engine speed limits Ne_min and Ne_max.

At 406, the CTC module 214 may calculate turbine speeds of a turbine(e.g., the turbine 301 of the torque converter 299 of FIG. 2) forrespective transmission ratios (or gears) for a current vehicle speed.As a result, a vector of n turbine speeds are obtained, where n is thenumber of transmission ratios (or gears). Table 1 is an example ofdifferent turbine speeds provided for different transmission ratios.

TABLE 1 Turbine Speeds for Transmission Gears Transmission Ratio (orGear) Turbine Speed 1 3000 . . . . . . N  600The ellipsis in Tables 1-6 refer to different transmission ratios and/orgears and corresponding parameters. In Tables 1-6, the values 1-n mayrefer to different transmission gears and/or transmission ratios, wheren is the total number of gears and/or the total number of transmissionratios available to select from.

At 408, the CTC module determines turbine torque values corresponding tothe turbine speeds obtained at 406 that satisfy a driver's power demandand/or the requested torque. As a result, a vector of n turbine torquevalues are obtained. Table 2 is an example of different turbine torquevalues for different turbine speeds provided for the differenttransmission ratios.

TABLE 2 Turbine Torques for Turbine Speeds Transmission Ratio (or Gear)Turbine Speed Turbine Torque 1 3000  36 . . . . . . . . . n  600 180

At 410, the CTC module 214 may, for each FF, add the correspondingachievable TCC slip to the turbine speeds obtained above to obtainrespective engine speeds. This is done while maintaining a same value ofturbine torque. Engine torque values may be determined based on theturbine torque values and for simplicity of explanation the enginetorque values are set equal to the turbine torque values. As a resultn*m pairs of engine speeds and engine torques are obtained, where m isthe number of firing fractions. Table 3 shows example engine speeds andengine torques.

TABLE 3 Engine Speed and Torque for Firing Fraction and TransmissionGear Firing Transmission Ratio Engine Engine Fraction (or Gear) SpeedTorque 1 1 3000  36 . . . . . . . . . n  600 180 . . . ½ 1 3005  36 . .. . . . . . . n  605 180 . . . ¼ 1 3007  36 . . . . . . . . . n  607 180. . .

At 412, the CTC module 214 determines fuel rates using engine fuel ratemaps for respective firing fractions and for the pairs of engine speedsand engine torques obtained at 410. If the engine speed and enginetorque pair is out of an operable range, then an infinite (or large)value is assigned. An example of this is shown in Table 4, whichincludes fuel rates for the engine speed and engine torque pairsobtained at operation 410. The fuel rate for the FF of ½ and the nthtransmission gear is outside of an operable range and thus the fuel ratevalue is set to a high predetermined default fuel rate value (e.g.,100000). Performance of operation 412 provides n*m fuel rate values.

TABLE 4 Engine Fuel Rates for Engine Speeds and Torques FiringTransmission Engine Engine Fuel Fraction Ratio (or Gear) Speed TorqueRate 1 1 3000  36 8 . . . . . . . . . n  600 180 7 . . . ½ 1 3005  367.9 . . . . . . . . . n  605 180 100000 . . . ¼ 1 3007  36 7.8 . . . . .. . . . n  607 180 7.4 . . .

At 414, the CTC module 214 determines the power transfer efficiencycorresponding to each engine speed and torque pair. The power transferefficiency, as defined above, refers to the transfer efficiency of powerfrom the engine to an output of the transmission. Table 5 includestransfer efficiency values for the engine speed and torque pairs.

TABLE 5 Transfer Efficiency Values for Engine Speeds and TorquesTransmission Firing Ratio (or Engine Engine Fuel Transfer Fraction Gear)Speed Torque Rate Efficiency 1 1 3000  36 8 0.91 . . . . . . . . . n 600 180 7 0.94 . . . ½ 1 3005  36 7.9 0.9 . . . . . . . . . n  605 180100000 0.91 . . . ¼ 1 3007  36 7.8 0.9 . . . . . . . . . n  607 180 7.40.91 . . .

At 416, the CTC module 214 calculates fuel efficiency valuescorresponding to each of the power transfer efficiency values. The fuelefficiency values may be determined using, for example, equation 2.

$\begin{matrix}{{engine\_ speed}*{engine\_ torque}*\frac{transfer\_ efficiency}{fuel\_ rate}} & (2)\end{matrix}$Table 6 includes example fuel efficiency values.

TABLE 6 Transfer Efficiency Values for Engine Speeds and Torques Trans-mission Transfer Fuel Firing Ratio (or Engine Engine Fuel Effi- Effi-Fraction Gear) Speed Torque Rate ciency ciency 1 1 3000 36 8 0.91 7.28 .. . . . . . . . n 600 180 7 0.94 14,503 . . . ½ 1 3005 36 7.9 0.9 12,324. . . . . . . . . n 605 180 100000 0.91 0.99 . . . ¼ 1 3007 36 7.8 0.912,491 . . . . . . . . . n 607 180 7.4 0.91 13,436 . . .

At 418, the CTC module 214 orders the parameter sets (e.g., parametervalues in each row of Table 6) based on fuel efficiency. The parametersets may be ordered in terms of fuel efficiency from high to low.

At 420, the CTC module 214 applies hysteresis and shift abilityconstraints and/or other drive ability constraints to the orderedparameter sets. This may include removing parameter sets that do notsatisfy the constraints and reordering remaining parameter sets based onthe fuel efficiency values.

At 422, the CTC module 214 selects one of the remaining transmissionratio and firing fraction pairs that (i) satisfies the minimum engineoutput torque to satisfy the total requested output torque, and (ii) hasthe best (or maximum) fuel efficiency relative to the other remainingtransmission ratio and firing fraction pairs. The CTC module 214 maysignal the transmission control module 294 to transition to thetransmission ratio (or gear) of the selected pair if not alreadyoperation at that ratio (or in that gear). The CTC module 214 may alsosignal the spark actuator module 226 to follow a firing patternassociated with the selected firing fraction. The signaling of themodules 294 and 226 may happen concurrently. Operation 402 may beperformed subsequent to operation 422.

The above described examples enlarge the optimization space in whichtransmission ratio and firing fractions pairs are selected and as aresult provide improved fuel efficiency. The disclosed fuel managementsystem may (i) select transmission ratio and firing fraction pairs nottraditionally selected, and/or (ii) operate with particular transmissionratio and firing fraction pairs during conditions in which traditionallyother less fuel efficient transmission gear and firing fraction pairsmay have been selected.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. It should be understood thatone or more steps within a method may be executed in different order (orconcurrently) without altering the principles of the present disclosure.Further, although each of the embodiments is described above as havingcertain features, any one or more of those features described withrespect to any embodiment of the disclosure can be implemented in and/orcombined with features of any of the other embodiments, even if thatcombination is not explicitly described. In other words, the describedembodiments are not mutually exclusive, and permutations of one or moreembodiments with one another remain within the scope of this disclosure.

Spatial and functional relationships between elements (for example,between modules, circuit elements, semiconductor layers, etc.) aredescribed using various terms, including “connected,” “engaged,”“coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and“disposed.” Unless explicitly described as being “direct,” when arelationship between first and second elements is described in the abovedisclosure, that relationship can be a direct relationship where noother intervening elements are present between the first and secondelements, but can also be an indirect relationship where one or moreintervening elements are present (either spatially or functionally)between the first and second elements. As used herein, the phrase atleast one of A, B, and C should be construed to mean a logical (A OR BOR C), using a non-exclusive logical OR, and should not be construed tomean “at least one of A, at least one of B, and at least one of C.”

In the figures, the direction of an arrow, as indicated by thearrowhead, generally demonstrates the flow of information (such as dataor instructions) that is of interest to the illustration. For example,when element A and element B exchange a variety of information butinformation transmitted from element A to element B is relevant to theillustration, the arrow may point from element A to element B. Thisunidirectional arrow does not imply that no other information istransmitted from element B to element A. Further, for information sentfrom element A to element B, element B may send requests for, or receiptacknowledgements of, the information to element A.

In this application, including the definitions below, the term “module”or the term “controller” may be replaced with the term “circuit.” Theterm “module” may refer to, be part of, or include: an ApplicationSpecific Integrated Circuit (ASIC); a digital, analog, or mixedanalog/digital discrete circuit; a digital, analog, or mixedanalog/digital integrated circuit; a combinational logic circuit; afield programmable gate array (FPGA); a processor circuit (shared,dedicated, or group) that executes code; a memory circuit (shared,dedicated, or group) that stores code executed by the processor circuit;other suitable hardware components that provide the describedfunctionality; or a combination of some or all of the above, such as ina system-on-chip.

The module may include one or more interface circuits. In some examples,the interface circuits may include wired or wireless interfaces that areconnected to a local area network (LAN), the Internet, a wide areanetwork (WAN), or combinations thereof. The functionality of any givenmodule of the present disclosure may be distributed among multiplemodules that are connected via interface circuits. For example, multiplemodules may allow load balancing. In a further example, a server (alsoknown as remote, or cloud) module may accomplish some functionality onbehalf of a client module.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes, datastructures, and/or objects. The term shared processor circuitencompasses a single processor circuit that executes some or all codefrom multiple modules. The term group processor circuit encompasses aprocessor circuit that, in combination with additional processorcircuits, executes some or all code from one or more modules. Referencesto multiple processor circuits encompass multiple processor circuits ondiscrete dies, multiple processor circuits on a single die, multiplecores of a single processor circuit, multiple threads of a singleprocessor circuit, or a combination of the above. The term shared memorycircuit encompasses a single memory circuit that stores some or all codefrom multiple modules. The term group memory circuit encompasses amemory circuit that, in combination with additional memories, storessome or all code from one or more modules.

The term memory circuit is a subset of the term computer-readablemedium. The term computer-readable medium, as used herein, does notencompass transitory electrical or electromagnetic signals propagatingthrough a medium (such as on a carrier wave); the term computer-readablemedium may therefore be considered tangible and non-transitory.Non-limiting examples of a non-transitory, tangible computer-readablemedium are nonvolatile memory circuits (such as a flash memory circuit,an erasable programmable read-only memory circuit, or a mask read-onlymemory circuit), volatile memory circuits (such as a static randomaccess memory circuit or a dynamic random access memory circuit),magnetic storage media (such as an analog or digital magnetic tape or ahard disk drive), and optical storage media (such as a CD, a DVD, or aBlu-ray Disc).

The apparatuses and methods described in this application may bepartially or fully implemented by a special purpose computer created byconfiguring a general purpose computer to execute one or more particularfunctions embodied in computer programs. The functional blocks,flowchart components, and other elements described above serve assoftware specifications, which can be translated into the computerprograms by the routine work of a skilled technician or programmer.

The computer programs include processor-executable instructions that arestored on at least one non-transitory, tangible computer-readablemedium. The computer programs may also include or rely on stored data.The computer programs may encompass a basic input/output system (BIOS)that interacts with hardware of the special purpose computer, devicedrivers that interact with particular devices of the special purposecomputer, one or more operating systems, user applications, backgroundservices, background applications, etc.

The computer programs may include: (i) descriptive text to be parsed,such as HTML (hypertext markup language), XML (extensible markuplanguage), or JSON (JavaScript Object Notation) (ii) assembly code,(iii) object code generated from source code by a compiler, (iv) sourcecode for execution by an interpreter, (v) source code for compilationand execution by a just-in-time compiler, etc. As examples only, sourcecode may be written using syntax from languages including C, C++, C#,Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl,Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5threvision), Ada, ASP (Active Server Pages), PHP (PHP: HypertextPreprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, VisualBasic®, Lua, MATLAB, SIMULINK, and Python®.

What is claimed is:
 1. A fuel management system comprising: a memoryconfigured to store m fuel rate maps respectively for m firingfractions, wherein each of the m firing fractions corresponds to arespective firing pattern for a plurality of cylinders of an engine of avehicle, wherein at least some of the firing patterns includedeactivating one or more of the plurality of cylinders, and where m isan integer greater than or equal to two; and a control module configuredto for each of the m firing fractions, determine a fuel efficiency valuefor each of n transmission gear ratios, wherein n*m fuel efficiencyvalues are provided for n*m transmission ratio and firing fractionpairs, applying a plurality of drive ability constraints to the n*mtransmission ratio and firing fraction pairs to provide resultanttransmission ratio and firing fraction pairs, subsequent to applying theplurality of drive ability constraints and based on the fuel efficiencyvalues of the resultant transmission ratio and firing fraction pairs,select one of the resultant transmission ratio and firing fractionpairs, and concurrently operate a transmission and the engine accordingto the selected one of the plurality of transmission ratio and firingfraction pairs.
 2. The fuel management system of claim 1, wherein: thecontrol module is configured to select the one of the resultanttransmission ratio and firing fraction pairs based on a cost function,which is directly related to fuel efficiency; and the cost function isbased on a fuel rate, an engine power, and a transfer efficiency.
 3. Thefuel management system of claim 1, wherein the control module isconfigured to: for each of the m firing fractions, determine a transferefficiency value for each of the n transmission gear ratios; anddetermine each of the n*m fuel efficiency values based on a respectiveone of the transfer efficiency values.
 4. The fuel management system ofclaim 3, wherein the control module is configured to determine each ofthe transfer efficiency values based on a respective engine speed andengine torque pair.
 5. The fuel management system of claim 1, whereinthe control module is configured to: for each of the m firing fractions,determine a fuel rate for each of the n transmission gear ratios; anddetermine each of the n*m fuel efficiency values based on a respectiveone of the fuel rates.
 6. The fuel management system of claim 5, whereinthe control module is configured to determine each of the fuel ratesbased on a respective one of a plurality of engine speed and enginetorque pairs.
 7. The fuel management system of claim 6, wherein thecontrol module is configured to: in response to determining one of theplurality of engine speed and engine torque pairs is outside of anoperable range, assign a predetermined default fuel rate value for acorresponding one of the n*m transmission ratio and firing fractionpairs; and refrain from selecting the one of the n*m transmission ratioand firing fraction pairs based on the predetermined default fuel ratevalue.
 8. The fuel management system of claim 1, wherein the controlmodule is configured to: for each of the m firing fractions, determinean engine speed and engine torque pair for each of the n transmissiongear ratios; determine a transfer efficiency value for each of theengine speed and engine torque pairs; and determine the n*m fuelefficiency values based respectively on the transfer efficiency values.9. The fuel management system of claim 1, wherein the control module isconfigured to: determine a turbine speed and turbine torque pair of atorque converter for each of the n transmission gear ratios; for each ofthe m firing fractions and based on an amount of torque converter slipand the turbine speed and turbine torque pairs, determine an enginespeed and engine torque pair for each of the n transmission gear ratios;determine a transfer efficiency value for each of the engine speed andengine torque pairs; and determine the n*m fuel efficiency values basedrespectively on the transfer efficiency values.
 10. The fuel managementsystem of claim 1, wherein the plurality of drive ability constraintscomprise at least one of: limiting output torque to a maximum amount ofengine output torque; limiting, for each of the m firing fractions,engine speed to be within a range between a minimum engine speed and amaximum engine speed; preventing concurrent deactivation of apredetermined combination of the plurality of cylinders; preventing apredetermined order of activating selected ones of the plurality ofcylinders; or preventing a predetermined order of deactivating selectedones of the plurality of cylinders.
 11. A fuel management methodcomprising: storing in a memory m fuel rate maps respectively for mfiring fractions, wherein each of the m firing fractions corresponds toa respective firing pattern for a plurality of cylinders of an engine ofa vehicle, wherein at least some of the firing patterns includedeactivating one or more of the plurality of cylinders, and where m isan integer greater than or equal to two; for each of the m firingfractions, determining a fuel efficiency value for each of ntransmission gear ratios, wherein n*m fuel efficiency values areprovided for n*m transmission ratio and firing fraction pairs; applyinga plurality of drive ability constraints to the n*m transmission ratioand firing fraction pairs to provide resultant transmission ratio andfiring fraction pairs; subsequent to applying the plurality of driveability constraints and based on the fuel efficiency values of theresultant transmission ratio and firing fraction pairs, selecting one ofthe resultant transmission ratio and firing fraction pairs; andconcurrently operating a transmission and the engine according to theselected one of the plurality of transmission ratio and firing fractionpairs.
 12. The fuel management method of claim 11, further comprisingselecting the one of the resultant transmission ratio and firingfraction pairs based on a cost function, which is directly related tofuel efficiency, wherein the cost function is based on a fuel rate, anengine power, and a transfer efficiency.
 13. The fuel management methodof claim 11, further comprising: for each of the m firing fractions,determining a transfer efficiency value for each of the n transmissiongear ratios; and determining each of the n*m fuel efficiency valuesbased on a respective one of the transfer efficiency values.
 14. Thefuel management method of claim 13, further comprising determining eachof the transfer efficiency values based on a respective engine speed andan engine torque pair.
 15. The fuel management method of claim 11,further comprising: for each of the m firing fractions, determining afuel rate for each of the n transmission gear ratios; and determiningeach of the n*m fuel efficiency values based on a respective one of thefuel rates.
 16. The fuel management method of claim 15, furthercomprising determining each of the fuel rates for a respective one of aplurality of engine speed and engine torque pairs.
 17. The fuelmanagement method of claim 16, further comprising: in response todetermining one of the plurality of engine speed and engine torque pairsis outside of an operable range, assigning a predetermined default fuelrate value for a corresponding one of the n*m transmission ratio andfiring fraction pairs; and refraining from selecting the one of the n*mtransmission ratio and firing fraction pairs based on the predetermineddefault fuel rate value.
 18. The fuel management method of claim 11,further comprising: for each of the m firing fractions, determining anengine speed and engine torque pair for each of the n transmission gearratios; determining a transfer efficiency value for each of the enginespeed and engine torque pairs; and determining the n*m fuel efficiencyvalues based respectively on the transfer efficiency values.
 19. Thefuel management method of claim 11, further comprising: determining aturbine speed and turbine torque pair of a torque converter for each ofthe n transmission gear ratios; for each of the m firing fractions andbased on an amount of torque converter slip and the turbine speed andturbine torque pairs, determining an engine speed and engine torque pairfor each of the n transmission gear ratios; determining a transferefficiency value for each of the engine speed and engine torque pairs;and determining the n*m fuel efficiency values based respectively on thetransfer efficiency values.
 20. The fuel management method of claim 11,wherein the plurality of drive ability constraints comprise at least oneof: limiting output torque to a maximum amount of engine output torque;limiting, for each of the m firing fractions, engine speed to be withina range between a minimum engine speed and a maximum engine speed;preventing concurrent deactivation of a predetermined combination of theplurality of cylinders; preventing a predetermined order of activatingselected ones of the plurality of cylinders; or preventing apredetermined order of deactivating selected ones of the plurality ofcylinders.